An experiment was carried out in 2005 in Yixing and Changshu,part of the Taihu Lake region,to study roles of buffer strips (BS) in reducing nitrogen (N) and phosphorus (P) concentrations in surface water,leachate,and irrigation water of paddy fields different in fertilization level during the rice-growing season,and their effect on yield of the crop,Results show that Treatment BS differed slightly from Treatment Fertilization in rice yield,but significantly reduced N and P loss by intercepting runoff,The total net N intercepted ranged between 20.6 and 51.9 kg hm^-2,accounting for 31.7%～50.9% of the total dis-solved N in the surface water,and the total net P intercepted did between 4.7 and 5.1 kg hm^-2,accounting for more than 1/2 of the total dissolved P in the surface water.Its role in intercepting N and P in leachate in soil profile was also apparent,reducing N and P transfer into water bodies.N and P concentrations in the profile display a declining trend with the depth,suggesting that paddy field can filter out N and P from irrigation water.